Match 5 board 14

NS reached 5C against us after the auction P 1H 1S 1NT 2S 3C P 3D P 4C P 5C.

W led a ♦ to the K and A.  Declarer tried a ♠ up immediately but W rose A.  Now declarer is threatening to ruff 2 hearts in dummy and pitch 2 on the ♠KQ.  So to stop that W switches to a trump.  Which one?

Had W been looking at Q10x the textbook play is the Q.  That appears to give up a trump trick but it comes back if declarer ruffs a ♥ in dummy with the ♣J as that promotes the 10 again.  In fact the Q also works here because partner's 10 gets promoted in the same way.

At the table W reasonably enough exited a low ♣ though which declarer won on the table with the J.  Now the defence prevail a different way.  Declarer can still pitch 2 hearts on the ♠KQ and can ruff one in dummy.  But then he has to leave dummy.  A ♦ is no good because W is ruffing that.  So he has to lead the 4th ♠.  But E ruffs that with the ♣10.  That uppercut promotes W's ♣Q back into a trick again.  Declarer must overruff (if he pitches his last ♥ instead, E just gives W a ♦ ruff).  Now there's nowhere for declarer's remaining ♥ loser to go so 10 tricks are the limit.  A fairly satisfying way for EW to earn +50.